The Chiefs beat the 49ers in Super Bowl LIV on Feb. 2. One day later, the U.S. declared COVID-19 a public health emergency.

The big picture: A lot has happened in the 223 days since then, highlighted by Tom Brady's arrival in Tampa Bay via free agency and Joe Burrow's arrival in Cincinnati via the NFL's first-ever virtual draft. Teams aced the training camp protocols, but without any preseason games, expect to see some rust when they finally take the field for game day.

What to expect: "The mayhem of the sideline will be replaced by a sparse smattering of players and coaches, who, like the on-field officials, will be wearing masks," writes WashPost's Adam Kilgore.

• Lots of protocols: Electronic whistles are in; cheerleaders, mascots and jersey swaps are out. Crowd noise will be piped in by audio mixers, and footballs will be rinsed with chemicals.
• Cavernous stadiums: Only six teams will allow fans in Week 1, and none will surpass 25% capacity. Those six teams: Browns (10%), Chiefs (22%), Colts (3%) Cowboys (TBD), Dolphins (20%) and Jaguars (25%).

Go deeper:

• 15 NFL coronavirus protocols you need to know (ESPN)
• The sound of silent NFL stadiums (The Ringer)
• How the coronavirus could impact NFL betting (Action Network)

Key storylines to watch

Player protests/social justice: In the wake of a summer filled with strikes and protests, NFL players are expected to keep the focus on race and social justice reform. End zones will be inscribed with two slogans: "It Takes All Of Us" on one side, "End Racism" on the other.

Expanded playoffs: Unlike baseball, the NFL's expanded playoffs are not a temporary measure devised for a pandemic season. Going forward, 14 teams (up from 12) will make the postseason and just the top seed (not top two) in each conference will earn a first-round bye.

Player shuffle: A host of current and former stars are rocking new jerseys, including Tom Brady (TB), Cam Newton (NE), Philip Rivers (IND), Stefon Diggs (BUF), David Johnson (HOU), DeAndre Hopkins (ARI), Melvin Gordon (DEN), Todd Gurley (ATL), Trent Williams (SF) and Calais Campbell (BAL).

Coaching shuffle: There are also five new head coaches: Kevin Stefanski (Browns), Ron Rivera (Washington), Joe Judge (Giants), Matt Rhule (Panthers) and Mike McCarthy (Cowboys).

PI is non-reviewable: Well, that was a fun experiment. After a missed call cost the Saints a 2019 playoff game, the league made a rule change allowing coaches to challenge pass interference. It failed miserably, so we're back to square one.

Rookie QBs: Only reigning Heisman winner Joe Burrow (Bengals) is slated to start Week 1, but we're likely to see Tua Tagovailoa (Dolphins) and Justin Herbert (Chargers) at some point, and maybe even Jordan Love (Packers).

SoFi Stadium: The Chargers and Rams' new shared stadium cost a record-breaking $5 billion. Unfortunately, fans are barred until 2021.

Raiders in Vegas: Oakland losing the Warriors and Raiders in consecutive years is inarguably cruel, but something about the Raiders in Sin City just makes sense. Their new stadium is a marvel, but fans will have to wait until next year to see it in person.

Preseason power rankings

Go deeper:Week 1 schedule

Sign up for my daily Axios Sports newsletter for more.